the Force of Fired Gzutpowder. 1 1 7 



its natural size, is 2.78 inches long, and 2.82 inches in 

 diameter at its lower extremity, where it reposes upon 

 its supporter, but something less above, being somewhat 

 diminished and rounded off at its upper extremity. Its 

 bore, which, as I have already observed, is \ of an inch 

 in diameter, is 2.13 inches long, and it ends in a very 

 narrow opening below, not more than 0.07 of an inch in 

 diameter, and 1.7 15 inch long, which forms the vent (if 

 I may be permitted to apply that name to a passage 

 which is not open at both ends), by which the fire is 

 communicated to the charge. From the center of the 

 bottom of the barrel there is a projection of about 0.45 

 of an inch in diameter, and 1.3 inch long, which forms 

 the vent tube V. Fig. 3 is a view of an iron ball W, 

 which, being heated red-hot, and being applied to the 

 vent tube by means of an hole O, made in it for that 

 purpose, fire is communicated through the solid sub- 

 stance of the vent tube to the powder it contains, and 

 from thence to the charge. 



Fig. 4, which is drawn on a scale of two inches to the 

 inch, or half the real size of the machinery, shews how 

 the barrel B was placed upon its support C, how this 

 last was placed upon its circular plate of iron D, and how 

 the red-hot iron ball W was applied to the vent tube V. 

 This ball is managed by means of a long handle /z, of iron, 

 and being introduced through a circular opening^, in the 

 support, and applied to the vent tube V, is kept in its 

 place by means of a wedge, or rather lever /, whose ex- 

 ternal end is represented in the drawing as being broken 

 off, to save room. The circular opening in front of the 

 support is seen in front, and consequently more dis- 

 tinctly, in the drawing, Fig. i. In this drawing the end 

 of the vent tube may be likewise discovered through 



